JP2021014075A - Film correction device, digital printer, and manufacturing method of printed plastic film matter - Google Patents

Abstract

To provide a film correction device capable of suppressing sagging and curling of a film during printing, in a digital printing method for printing information, such as characters or images, on a surface of the plastic film according to an inkjet method.SOLUTION: A film correction device suppresses sagging and/or curling of a film arranging two rolls for feeding the film forward while rotating and suctioning, that are orthogonal to a conveyance direction of the film, so as to be located before and after an ink head part at a lower part of the ink head during digital printing for performing printing according to an inkjet method on a surface of the plastic film. Further, the film correction device corrects sagging and/or curling of the plastic film 1, and includes: a pair of cylindrical bodies 5 and 6 having suction holes; a rotary mechanism for rotating the pair of cylindrical bodies respectively in the conveyance direction of the film; and a suction mechanism for suctioning the film through the suction holes of the cylindrical bodies.SELECTED DRAWING: Figure 1

Description

The present invention relates to a digital printing method in which a block copy does not need to be produced as in gravure printing and offset printing, and is printed by directly spraying atomized ink onto a printing medium such as a plastic film. It relates to a device capable of effectively preventing sagging and curling.

Conventionally, gravure printing has been the mainstream for printing on plastic films, specifically multilayer plastic films. On the other hand, digital printing, which enables high-definition and high-resolution printing, has been introduced into the film industry since around 2007. Unlike gravure printing, digital printing does not require the creation of block copy, so it is characterized by low manufacturing costs. In addition, since the ink that has been atomized by the inkjet method is directly sprayed for printing, vivid and beautiful printing is possible. Further, it is possible to print in a wide variety of small lots, and for example, it is possible to provide a packaging body having a different pattern depending on the season. Currently, it has been put into practical use mainly as a back print on stretched PET films, OPPs, and the like.

However, a problem in such digital printing is the slack and curl of the plastic film as the printing medium. In the conventional gravure printing, the film is pressed against the plate cylinder for printing, so that there is no problem even if the film has some slack or curl. However, in digital printing, since the film is advanced only by the guide roll, there is nothing that suppresses the slack and curl of the film, and the distance between the ink head and the film at the time of printing is currently only a few millimeters, 1 to 2 mm. The slack part of the film rubs against the ink head. In the case of the continuous type, which continuously discharges ink even in digital printing, the distance between the ink head and the film can be increased, so the film does not rub the ink head, but the printed characters and images are distorted. And the product cannot be shipped.

Various proposals have been made for improving the film itself as a method for suppressing sagging and curling of the film (see, for example, Patent Documents 1 and 2).

International Publication No. 2018/11039 Japanese Unexamined Patent Publication No. 2003-175543

However, it is only necessary to have a device that suppresses the slack and curl of the film without improving the film itself, but a device that suppresses the slack and curl of the film is particularly suitable for digital printing. The current situation is that no proposal has been made yet.

Therefore, an object of the present invention is to provide a film straightening device capable of suppressing sagging and curling of a film during printing in a digital printing method in which information such as characters or images is printed on the surface of a plastic film by an inkjet method. The purpose is.

As a result of diligent studies to achieve the above object, the present inventors have found that the sagging and curling of a film at the time of printing can be suppressed by using a specific film straightening device. The present invention has been completed based on these many years of knowledge.

That is, in the present invention, two rotations and suctions perpendicular to the transport direction of the film are located at the lower part of the ink head during digital printing on the surface of the plastic film by the inkjet method so as to be located in front of and behind the ink head portion. Provided is a film straightening device that suppresses slack and / or curl of a film while installing a roll that feeds the film forward.

In one embodiment of the film straightening apparatus of the present invention, a suction portion is devised so that the roll rotates in synchronization with the printing speed to feed the film forward. As a result, the rotation speed of the roll can be controlled, and the transfer speed of the film is not hindered.

Although it is the installation position of the roll, it is installed only at the bottom of the ink head.

By rotating the roll in the film transport direction (film traveling direction), the film is transported forward. Further, by evacuating the inside of the roll and forming a suction hole in the roll, the film can be sucked, and it can be expected that the slack and curl of the film are suppressed.

Further, the present invention is a film straightening device for correcting slack and / or curl of a plastic film, in which a pair of tubular bodies having suction holes and the pair of tubular bodies are rotated in the film transport direction, respectively. The first transport roll is provided with a rotation mechanism for sucking the film from the suction holes of the tubular body, and the pair of tubular bodies transports the film to the ink head portion for digital printing. A film straightening device, which is a second transport roll for winding a film digitally printed by the ink head portion, is provided.

It is preferable that each of the pair of tubular bodies has a plurality of suction holes in the circumferential direction of the tubular body.

It is preferable that the pair of tubular bodies are provided so as to be located in front of and behind the ink head portion.

It is preferable that the pair of tubular bodies are provided so as to be orthogonal to the film conveying direction.

The plastic film is preferably a multilayer film having a thickness of 30 to 100 μm.

Further, in the present invention, an upstream guide roll that unwinds and conveys a roll-shaped plastic film, an ink head that digitally applies ink onto the plastic film, and the ink-coated plastic film are moved downstream. Provided is a digital printing machine comprising a downstream guide roll for carrying, and each of the upstream guide roll and the downstream guide roll has a suction hole for sucking the plastic film.

Further, in the present invention, while transporting a plastic film, the film straightening device suppresses slack and / or film curl in the transport direction, and ink is applied onto the film by digital printing to form a printing layer. Provided is a method for producing a plastic film printed matter, which comprises a printing step of forming the above.

As described above, the film straightening apparatus of the present invention can be preferably applied to a plastic film, and is particularly effective for printing on a multilayer plastic film having slack and curl. By preventing sagging and curling of the film and improving the flatness of the film during printing, information such as images can be brought into close contact with each other.

According to the film straightening apparatus of the present invention, slack and curl of the plastic film can be suppressed. Therefore, it is possible to perform digital printing with excellent aesthetics on a plastic film having slack or curl, particularly a multilayer plastic film.

It is a perspective view which shows one Embodiment of the film straightening apparatus of this invention. It is sectional drawing which shows the mechanism which eliminates the sagging of a film by using the film straightening apparatus of this invention. It is a top view which shows one Embodiment of the arrangement of the suction hole of the tubular body used in the film straightening apparatus of this invention. It is a top view which shows the other embodiment of the tubular body used for the film straightening apparatus of this invention. It is a top view which shows the other embodiment of the tubular body used for the film straightening apparatus of this invention.

The film straightening apparatus of the present invention has two rotations perpendicular to the transport direction of the film so as to be located in front of and behind the ink head portion at the lower part of the ink head during digital printing when printing on the surface of a plastic film by an inkjet method. A device for suppressing slack and / or curling of a film, which installs a roll that feeds the film forward while sucking. The film straightening device of the present invention is, for example, a film straightening device that straightens slack and / or curl of a plastic film, and transports a pair of tubular bodies having suction holes and the pair of tubular bodies, respectively. At least a rotation mechanism for rotating the film in the direction and a suction mechanism for sucking the film from the suction hole of the tubular body are provided. The pair of tubular bodies is a first transport roll for transporting the film to the ink head portion for digital printing and a second transport roll for winding the film digitally printed by the ink head portion.

FIG. 1 shows an embodiment of the film straightening apparatus of the present invention. FIG. 1 shows an embodiment in which the film straightening apparatus of the present invention is applied to an inkjet printing machine which is a kind of digital printing machine. 1 is a plastic film (hereinafter, may be simply referred to as "film"), 2 is an ink head, 3 is a winding side film roll, 4 is a winding side film roll, 5 is an upstream guide roll, and 6 is a downstream side. A guide roll, 7 is a winding part, 8 is a coating part, and 9 is a winding part.

In FIG. 1, the space is divided into the unwinding portion 7, the coating portion 8, and the winding portion 9 in the X-axis direction. The unwinding portion 7 is provided with an unwinding side film roll 3 and an upstream side guide roll 5 that are rotationally driven by an unwinding side motor (not shown) arranged in sequence in the X-axis direction. The take-up portion 9 is provided with a downstream guide roll 6 and a take-up side film roll 4 arranged in sequence in the X-axis direction. The guide rolls 5 and 6 are located before and after the coating portion 9 (specifically, before and after the ink head 2 portion), respectively, and are installed so as to feed the film 1 in the transport direction while rotating and sucking.

The guide roll 5 is the first transfer roll, and the guide roll 6 is the second transfer roll. That is, in the film transport direction, the first transport roll is a transport roll located immediately before the ink head 2, and no other roll is installed between the first transport roll and the ink head 2. Further, in the film transport direction, the second transport roll is a transport roll located immediately after the ink head 2, and no other roll is installed between the second transport roll and the ink head 2.

In the unwinding portion 7, the film 1 to be coated with the ink in the coating portion 8 is wound around the unwinding side film roll 3 in a roll shape. Further, the film 1 is unwound from the unwinding side film roll 3, passes through the coating portion 8, and is wound around the winding side film roll 4 by the winding portion 9. In such a state, the transport direction of the film 1 is the X-axis direction, the orthogonal direction (width direction) thereof is the Y-axis direction, and the direction perpendicular to the surface is the Z-axis direction.

In the coating portion 9, while the film 1 is conveyed in the X-axis direction, the printing ink is ejected from the ink head 2 while the slack and curl of the film 1 are eliminated by the guide rolls 5 and 6 which are a pair of tubular bodies. For example, printing is continuously performed on the film 1 by an inkjet method to form a printing layer. The guide rolls 5 and 6 are connected to a rotation mechanism for rotating the film 1 in the transport direction and a suction mechanism for sucking the film 1 from the suction holes of the guide roll (not shown). The film straightening device of the present invention includes at least such a pair of tubular bodies (guide rolls), the rotation mechanism, and the suction mechanism.

In the embodiment shown in FIG. 1, the guide rolls 5 and 6 are installed under the film 1 in front of and behind the ink head 2 so as to feed the film forward (in the transport direction) while rotating and sucking. That is, the guide rolls 5 and 6 are provided in the lower part of the film 1 located in the lower part of the ink head 2 of the inkjet printing machine at positions where the film 1 can be sucked in parallel with the width direction in the film transport direction. The guide rolls 5 and 6 each have a suction hole (through hole) on the surface, and the tubular body is installed so as to rotate in the transport direction of the film 1. Specifically, the guide rolls 5 and 6 are installed so as to rotate in the r1 direction, respectively. Then, the guide rolls 5 and 6 can stretch the film 1 back and forth in the transport direction by rotating in the r1 direction while sucking the back surface of the plastic film 1 from the suction holes provided on the front surface, respectively. The slack and / or curl of the film 1 between the rolls 5 and 6 can be eliminated.

FIG. 2 describes a mechanism for correcting slack in a film using the film straightening device of the present invention. FIG. 2 is a schematic cross-sectional view in the film transport direction for showing a mechanism for eliminating the slack of the film by using the film straightening device of the present invention. As shown in FIG. 2A, the film 1 at the stage of being conveyed onto the guide rolls 5 and 6 has a slack S in the conveying direction of the film 1. The slack S is a slack in the lower direction, but the film 1 may have a slack in the upper direction, or may have a slack in the lower direction in some parts and a slack in the upper direction in another part. is there. The downstream guide roll 6 rotates in the rotation direction r1 while sucking the back surface of the film 1 from the suction hole 61. Then, the upstream guide roll 5 sucks the back surface of the film 1 and rotates in synchronization with the rotation of the guide roll 6. As a result, as shown in FIG. 2B, the film 1 sucked (sucked) into the suction holes 51 and 61 is pulled back and forth in the transport direction, and the slack S is eliminated. Since the film 1 is unwound from the unwinding film roll 3 and continuously conveyed, the film 1 is continuously conveyed onto the guide rolls 5 and 6. Therefore, the guide rolls 5 and 6 continuously rotate in the transport direction to continuously eliminate the slack and curl of the film.

In the film straightening apparatus of the present invention, the position where the pair of tubular bodies is provided is preferably the lower part of the film as shown in FIG. 1, but the present invention is not limited to this mode, and the pair is provided on the upper part of the film. May be good. In this case, the guide rolls 5 and 6 do not have a suction port, and a tubular body having a suction hole that rotates in the film transport direction is provided above the guide rolls 5 and 6 with the film 1 interposed therebetween. .. In this case, since the pair of tubular bodies are rotated in the direction in which the film is conveyed, the tubular bodies are installed so as to rotate in the direction in which the film is conveyed, as in the case of providing the lower portion of the film. The specific direction of rotation of the tubular body when installed is opposite to r1 shown in FIG.

The upstream guide roll 5 and the downstream guide roll 6 are provided along the Y-axis direction and parallel to each other in the X-axis direction. It is preferable that the upstream guide roll 5 and the downstream guide roll 6 have substantially the same length (same or slightly longer than one).

When the film straightening device of the present invention is applied to a digital printing machine (particularly an inkjet printing machine), as shown in FIG. 1, the pair of tubular bodies are respectively located before and after the ink head of the inkjet printing machine. , Preferably provided at the bottom of the film. That is, it is preferable that the film straightening apparatus of the present invention has a pair (for example, 4 pairs in the case of a CMYK inkjet printing machine) for each ink head. Further, when the distance between the ink heads is short, it is sufficient to install one tubular body between the ink heads. In this case, before the front ink head, after the last ink head, and between the ink heads, respectively. It is also possible to install a tubular body. As a result, it is possible to prevent the film from sagging or curling only when the ink is directly sprayed. In this case, the position of the tubular body is appropriately set according to the size of the ink head.

In the film straightening device of the present invention, it is sufficient that the tubular body can suck the film in order to suck the film during operation, and even if the setting is such that the film cannot be sucked when not in operation. Good.

For example, when the coating target area of the film 1 reaches the coating portion 9, the suction holes of the guide rolls 5 and 6 are set in a state where vacuum suction is possible, and the operation for applying the ink to the coating target area of the film 1. Starts, the suction mechanism of the guide rolls 5 and 6 is operated while the film 1 is under tension in the X-axis direction, and the film 1 is vacuum-sucked to correct curl and slack. The suction mechanism of the guide rolls 5 and 6 may be stopped before the coating target region of the film 1 reaches the coating portion 9 and after passing through the coating portion 9.

The pair of tubular bodies is preferably a cylindrical body from the viewpoint of functioning as a guide roll, but may be a polygonal tubular body as long as the effects of the present invention are not impaired.

FIG. 3 shows a schematic top view of an embodiment of the guide roll 5. The guide roll 5 is provided with a plurality of suction holes 51 on its surface. The plurality of suction holes 51 are particularly evenly spaced in the circumferential direction (film transport direction, X-axis direction) of the rotation direction r1 of the guide roll 5 and in the direction orthogonal to the rotation direction r1 (width direction, Y-axis direction), respectively. It is equipped with. The guide roll 6 is also provided with a plurality of suction holes 61 like the guide roll 5, and one embodiment of the arrangement is the same as that of the guide roll 5. Since the guide rolls 5 and 6 are provided with the plurality of suction holes 51 and 61 in the circumferential direction, the guide rolls 5 and 6 rotate in the rotation direction r1 to suck the back surface of the film and curl. At the same time, the film can be smoothly conveyed in the conveying direction.

Further, it is preferable that the plurality of suction holes 51 and 61 are continuously provided along the circumferential direction (X-axis direction) of the guide rolls 5 and 6, respectively, particularly at equal intervals. As a result, the slack and curl of the film can be continuously eliminated at a gentle rotation speed. In particular, it is preferable that the plurality of suction holes 51 and 61 are provided in parallel in the circumferential direction and the width direction, respectively, as shown in FIG.

The hole diameters (diameters) of the suction holes 51 and 61 may be any as long as they can sufficiently suck the film and can suck the film in the transport direction (X-axis direction), and are, for example, 2 to 10 mm, preferably 2 to 10 mm. It is about 3 to 5 mm. When the hole diameter is 2 mm or more (particularly 3 mm or more), the suction force becomes sufficient, and slack and curl can be suppressed more effectively. When the pore diameter is 10 mm or less (particularly 5 mm or less), the suction force does not become too high, and the film can be conveyed more appropriately in the conveying direction.

The shape of the suction holes 51 and 61 is preferably circular, but may be polygonal as long as the effects of the present invention are not impaired.

When it is desired to change the suction strength, it is preferable to increase the number of suction holes rather than increasing the size of the suction holes. For example, when the diameter of the tubular body is 30 mm, it is preferable to prepare suction holes at intervals of 5 to 50 mm. However, since the degree of suction changes depending on the diameter of the tubular body, it is necessary to select it appropriately. The [distance between suction ports (distance between centers of adjacent suction ports) / outer diameter of the tubular body] is, for example, 0.1 to 0.8, preferably 0.15 to 0.6.

When it is difficult to increase the number of suction holes, a part of the tubular body can be made into a mesh plate 52, for example, as in the guide roll 5 shown in FIGS. 4 and 5. The net plate 52 also corresponds to the suction hole. As a result, it is possible to increase the suction force without changing the degree of vacuum. In the guide rolls 5 shown in FIGS. 4 and 5, the arrangement of the net plate 42 is not particularly limited and can be changed as appropriate. For example, the net plates 52 shown in FIGS. 4 and 5 may be arranged so as to be symmetrical or vertically symmetrical. Further, the arrangement of the net slab on the guide roll 6 is preferably the same as the arrangement on the guide roll 5, but may be different.

The material of the tubular body is not particularly limited, but stainless steel and plastic are preferable. Further, it is more preferable to have antistatic performance. The diameter (diameter) of the tubular body can be appropriately selected according to the size of the digital printing machine, but is preferably 25 to 100 mm, more preferably 50 to 70 mm.

The film straightening apparatus of the present invention satisfactorily eliminates slack and side curls of a film without providing a film support between the pair of tubular bodies at the lower part of the film, for example, the lower part of an ink head where slack is likely to occur. be able to.

The plastic film used in the film straightening apparatus of the present invention is not particularly limited, but is preferably a multilayer film (particularly, a multilayer coextruded film). This is because the multilayer film (particularly, the multilayer coextruded film) often has an asymmetrical structure in the thickness direction due to differences in the resin component and the thickness ratio of each layer, and slack and curl are likely to occur. The plastic film may be a sheet-shaped film (flat film) or a film in which a tubular film is flattened.

The thickness of the plastic film is not particularly limited, but is preferably 30 to 100 μm. The film straightening apparatus of the present invention is particularly suitable for eliminating slack and curl of a plastic film having such a thickness.

The film straightening device of the present invention can temporarily eliminate the slack and curl even if the film has slack and curl, regardless of the improvement of the film. Therefore, for example, as shown in FIG. 1, it is particularly preferable to use it in combination with a digital printing machine such as an inkjet printing machine. The usage mode of the film straightening device of the present invention is not limited to this, and can be applied to any device for eliminating slack and side curl of the film. For example, it can be preferably used for the purpose of temporarily eliminating slack and curl of a film when laminating with another film.

A plastic film printed matter can be produced by using the film straightening device and the digital printing machine of the present invention. Specifically, while transporting a plastic film, while suppressing slack and / or curling of the film in the transport direction, ink is applied onto the film by digital printing (for example, an inkjet method) to form a print layer. A plastic film printed matter can be produced by a method having a printing process.

The transport speed of the plastic film is not particularly limited, but is preferably 150 m / min or less from the viewpoint of eliminating slack and curling and printing at the same time.

The degree of vacuum when the film is sucked from the suction holes by the pair of tubular bodies is appropriately set according to the number of suction holes and the hole diameter, but is preferably 12 to 40 kPa. However, since the degree of suction differs depending on the width and thickness of the film, it is preferable to be able to adjust it according to the situation.

The rotation speed of the tubular body is preferably a drive structure that can be synchronized with the printing speed, but is preferably 20 to 80 rpm. However, it should be selected appropriately according to the diameter of the tubular body.

Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to these Examples. A plastic film was prepared as a printing medium. The details of the film are as follows.
-Film A: Multi-layer coextruded flat film A (composition: nylon / adhesive layer / polyethylene, thickness: 50 μm)
-Film B: Multi-layer coextruded tube film B (composition: nylon / adhesive layer / polyethylene, thickness: 50 μm)
-Film C: Multi-layer coextruded tube film C (with side seal, composition: nylon / adhesive layer / polyethylene, thickness: 50 μm)

Examples 1-3
The films A to C were digitally printed by an inkjet method using the film straightening apparatus shown in FIG. 1 while eliminating the slack and curl of the film to prepare a plastic film printed matter. The film transport speed is 50 mm / min according to the printing speed, the rotation speed of the pair of tubular bodies is 40 rpm, and the degree of vacuum inside the tubular bodies is 36 kPa. As the tubular body, as shown in FIG. 3, a pair of tubular bodies provided with a plurality of suction holes in the circumferential direction and the width direction were used. The diameter of the tubular body is 30 mm.

Comparative Examples 1-3
The films A to C were digitally printed by an inkjet method in the same manner as in Examples 1 to 3 except that the film straightening device was not used, to produce a plastic film printed matter.

(Evaluation)
The slack, curl, and rubbing against the ink head of the film were evaluated during digital printing performed in Examples and Comparative Examples. The criteria for each evaluation are as follows. The results are shown in Table 1.

(1) Slack and curl The case where the slack or curl was eliminated at the time of printing was evaluated as ◯, the case where the slack or curl was relatively small was evaluated as Δ, and the case where the slack or curl was relatively large was evaluated as ×.

(2) Rubbing with the ink head The case where the rubbing between the ink head and the film did not occur during printing was evaluated as ◯, and the case where the rubbing occurred was evaluated as x.

As can be seen from Table 1, by using the film straightening apparatus of the present invention, both the flat film and the tube film were prevented from sagging and curling, and no rubbing with the ink head was confirmed. Further, when the same film was used and the film straightening device of the present invention was not used, the curl of the tube film was not confirmed to be about that of a flat film, but as with the flat film, it slackened to the upper part (ink head side). Was confirmed, so rubbing against the ink head was also confirmed.

As a summary of the above, the configuration of the present invention and its variations thereof will be added below.
[1] A film straightening device that suppresses slack and / or curl of a film during digital printing by printing on the surface of a plastic film by an inkjet method.
[2] The film straightening apparatus according to [1], wherein two rotations orthogonal to the transport direction of the film and rolls for feeding the film forward while sucking are installed so as to be located in front of and behind the ink head portion.
[3] A film straightening device for correcting slack and / or curl of a plastic film, which is a rotation for rotating a pair of tubular bodies having suction holes and the pair of tubular bodies in the film transport direction. A film straightening device provided with a mechanism and a suction mechanism for sucking a film from the suction holes of the tubular body.
[4] The pair of tubular bodies is a first transport roll for transporting a film to an ink head portion for digital printing and a second transport roll for winding a film digitally printed by the ink head portion. 3] The film straightening device according to.
[5] No other roll is installed between the first transfer roll and the ink head, and no other roll is installed between the second transfer roll and the ink head. [3] ] Or the film straightening apparatus according to [4].
[6] The film straightening apparatus according to any one of [3] to [5], wherein each of the pair of tubular bodies has a plurality of suction holes in the circumferential direction of the tubular body.
[7] The film straightening apparatus according to any one of [3] to [6], wherein the pair of tubular bodies are installed so as to be orthogonal to the film conveying direction.
[8] The film straightening apparatus according to any one of [3] to [7], which does not have a film support between the pair of tubular bodies.

[9] The film straightening apparatus according to any one of [1] to [8], wherein the plastic film is a multilayer film having a thickness of 30 to 100 μm.
[10] An upstream guide roll that unwinds and conveys a roll-shaped plastic film, an ink head that digitally applies ink onto the plastic film, and a roll-shaped plastic film that carries and conveys the ink-coated plastic film. A digital printing machine comprising a downstream side guide roll for winding up the upstream side guide roll and the downstream side guide roll each having suction holes for sucking the plastic film.
[11] While transporting the plastic film, the film by digital printing while suppressing the slack and / or the film curl in the transport direction by the film straightening device to any one of [1] to [9]. A method for producing a plastic film printed matter, which comprises a printing process of applying ink on the film to form a printing layer.

The film straightening apparatus of the present invention can perform digital printing for printing information such as characters or images having excellent aesthetics by an inkjet method even on a plastic film having slack or side curl.

1 Plastic film 2 Ink head 3 Unwinding side film roll 4 Winding side film roll 5 Upstream side guide roll (cylindrical body)
6 Downstream guide roll (cylindrical body)
7 Unwinding part 8 Coating part 9 Winding part 51, 61 Suction hole 52 Net plate

Claims (7)

Two rotations perpendicular to the transport direction of the film, in front of the film while sucking, so that they are located in front of and behind the ink head at the bottom of the ink head during digital printing, which is printed on the surface of the plastic film by the inkjet method. A film straightening device that suppresses slack and / or curl of the film on which the feed roll is installed. A film straightening device that corrects slack and / or curl of a plastic film, a pair of tubular bodies having suction holes, a rotation mechanism for rotating the pair of tubular bodies in the film transport direction, and a rotation mechanism. The pair of tubular bodies include a suction mechanism for sucking the film from the suction holes of the tubular body, and the pair of tubular bodies includes a first transport roll for transporting the film to an ink head portion for digital printing and the ink head portion. A film straightening device, which is a second transport roll that winds up a film digitally printed by. The film straightening apparatus according to claim 2, wherein each of the pair of tubular bodies has a plurality of suction holes in the circumferential direction of the tubular body. The film straightening apparatus according to claim 2 or 3, wherein the pair of tubular bodies are installed so as to be orthogonal to a film conveying direction, respectively. The film straightening apparatus according to any one of claims 1 to 4, wherein the plastic film is a multilayer plastic film having a thickness of 30 to 100 μm. An upstream guide roll that unwinds and conveys a roll-shaped plastic film, an ink head that digitally applies ink onto the plastic film, and a downstream guide roll that conveys the ink-coated plastic film downstream. And with
The upstream side guide roll and the downstream side guide roll are digital printing machines each having suction holes for sucking the plastic film. While transporting the plastic film, apply ink on the film by digital printing while suppressing slack and / or film curl in the transport direction by a film straightening device according to any one of claims 1 to 5. A method for producing a plastic film printed matter, which comprises a printing step of forming a printing layer.

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